A reference herein to prior art is not to be taken as an admission that the prior art was known or that it was part of the common general knowledge as at the priority date of any of the claims.
Screening apparatus of the type with which the invention is concerned is generally used for screening, grading, or separating materials such as ores and comprises an array of screen panels which are removably fixed to a frame to provide a continuous screen deck. The material to be screened is fed onto the deck at one end and the apparatus is vibrated so that the material moves over and through its screening surface.
The screen panels in a screen deck are usually subject to wear, due to the abrasiveness of the mining materials typically being screened, and thus the screens require periodical replacement. This presents a difficulty with the attachment of the panels to the deck frame, as the attachment must be secure and robust and easily made, but it should also be releasable in a manner that is quick and easy. Applicant has developed several different forms of screen panel attachments, examples of which can be found in Australian patent no. 2012201297 and Australian patent no. 2012208984.
In addition to the need for screen panels to be easily attachable and releasable to and from a screen deck, screen panels should also be firmly secured in place on the deck and the screen array should not present or at least minimise gaps for passage of screening product or media other than through the openings formed in the screens themselves. If gaps do exist, then incorrect grade screening product can pass through the deck, or the screening product can become embedded between components of the screening deck and can cause wear. This can result in the need to clean parts of the vibratory machine or replace parts, either of which results in downtime of the vibratory machine.
Screen decks are therefore formed with either the side edges of adjacent screen panels abutting, or with cover strips employed between adjacent screen panels to overlie any gaps between the adjacent side edges. The present invention relates to screen decks that employ such cover strips.
By the use of cover strips, a screen deck can thus usually be formed without any gaps between adjacent panels being open for passage of screening product or media. That is, if gaps exist, the cover strips will overlie the gaps so that the screening product or media cannot enter the gaps.
Prevention of the entry of screening product or media into gaps between adjacent panels can also be provided by cover strips even if there is movement of the screen panels relative to one another during operation of the vibratory machine that causes gaps to be formed that were not formed prior to the vibratory machine being operated. For example, gaps that were not present when the screen panels were put in place can form once the vibratory machine is operated and the screen panels are subject to vibratory motion.
One form of movement that can create gaps is movement of screen panels in the direction of travel of the screening product over the screening deck. This type of movement is more likely to occur in so-called multi-slope or “banana” screening decks, in which the lead or initial section of deck is inclined or curved to increase the speed of the screening product across the initial section of the screening deck. Such screening decks can also provide other benefits or effects such as to promote water shedding from the screening product and so their use is often preferred. In that inclined or curved section of the screening deck, the screening product moves at high speed and the forces associated with that movement tends to push the screen panels in the direction that the screening product travels. If the screen panels move under that load, gaps between panels can arise.
The present invention seeks to provide a new arrangement in which cover strips are employed and which in some forms of the invention, with use of those cover strips, movement of screen panels in the manner described above is minimised or eliminated. The elimination of movement is intended once the screen panels have been finally positioned, such that in some forms of the invention, movement of the screen panels is advantageously allowed for installation purposes, but movement is prevented once the panels have been installed.